Lubrication of sliding bearings in steam engines, in 1813
Tallow and oil
In Abraham Rees's magnum opus, "The Cyclopædia; or universal Dictionary of Arts, Sciences and Literature"; Rees, A.; Longman, Hurst, Rees, Orme & Brown, London; 1802-1820, there's hardly any information to be found on lubrication of bearings as such.
Oil is mentioned, of course, particularly for fast-running journals; and tallow for slowly-moving ones. Further details are lacking. And, not unimportant, what exactly was meant by "fast-running journals" and "slowly-moving ones"?
What kind of engine speeds were common in the early 19th century? Most engines then were beam engines and they operated at anything from 15-20 revolutions per minute. Watt's sun-and-planet motion doubled the speed of the main shaft to 30-40 r.p.m.; but by 1800 this mechanism was obsolete and all beam engines had regular crank mechanisms.
A second class of engines, beside beam engines, are the small high-pressure direct-acting steam engines, mostly vertical at that time. These run at speeds of up to 30 r.p.m.
Now speeds of up to 30 r.p.m. were known long before the advent of the steam engine, in windmills and water mills. Lubrication with ordinary animal tallow was common for these. To improve lubrication, the tallow could be mixed with oil. This however destroyed one great advantage of tallow: its stiffness. Tallow would not easily run out of a bearing. Mixed with oil, it did.
In the early 19th c. beam engines, slow-moving as these were, there was no great need to deviate from mill-practice. Nearly all the engine's bearings were lubricated with tallow, as were the hempen piston and piston-rod packings. Only the main bearings required more advanced techniques. These were lubricated with oil and to this end, they were provided with oil cups, with cotton wicks; or, for larger engines, with oil tanks on top of the bearing caps, with adjustable drip feeds. The small direct-acting engines of the early 19th c. were usually lubricated in the same way as the beam engines and this proved to be one of their weak points. They required (too) much attention and special care from the engineer.
What oil exactly?
But, what kind of oil is Rees referring to? To answer that question, we'll have a look at the lemma "Oil" in the Cyclopædia. This appears in Volume 25, Section I (1813). Rees discernes two types.
A. Animal oils
Most animals contain oil and fat. The fat investing the kidneys of quadrupeds is called suet or tallow, and is the hardest and most solid of any. The next in hardness is the fat of the bones; and the fat in which the muscles are imbedded is the next in degree. The fat of the hog, called "lard", is the least solid. The fat or oil of fish is almost always fluid at the common temperature.
All the animal oils (and fats) belong to the class of unctuous or fat oils, none of them being either drying or capable of being dried by other substances. They are of very great economical importance. They are used as food, and in medicine as the basis for onguents; they are largely employed in the manufacture of soap; and also for burning either in lamps or in the form of candles. Fish oils always are rancid and mostly thick and glutinous. This renders them less suitable for burning in lamps.
Rees does not mention the use of animal oil for the lubrication of machinery.
B. Vegetable oils
Vegetable oils are divided into two classes: (A), Volatile oils and (B), Fixed oils.
1. Volatile vegetable oils
Of great use in medicine. They are considered stimulants. They are also used as perfumes; and in the composition of varnishes and paints. Due to their volatility, the essential oils are of no interest for lubricating purposes.
2. Fixed vegetable oils
In contrast to the volatile vegetable oils, they cannot be directly volatilized without decomposition. When these fixed oils are boiled, a vapour is disengaged consisting of oil, carburetted hydrogen and carbonic acid. When finally every thing volatile has been driven off, nothing remains in the vessel but a little charcoal. The oil that was driven off, when condensed, is lighter, less viscous and more volatile than the original oil. By continuing this process of boiling and condensing, all oil can be made to disappear, only some charcoal remaining.
The most common fixed vegetable oils are procured from the cotyledons of rape seed and linseed. The seeds are beaten to a pulp and then heated to a certain temperature. The mass is then subjected to the action of a strong press, to force out the oil.
Fixed vegetable oils are divided into two sub-orders: (a), Drying oils and (b), Fat oils.
a. Drying vegetable oils
When a drying vegetable oil is exposed to the air for a certain time, it gradually acquires properties similar to those of horn by the action of oxygen, becoming a concrete, flexible and hard substance.
The two most important oils of the drying kind are those extracted from lin-seeds and hemp-seeds. Both hempseed oil and linseed oil are of great use for paints and varnishes and making printers' ink. It will be clear, that drying oils cannot be used in bearings, as they would quickly gum these up.
b. Fat vegetable oils
When a fat vegetable oil is exposed to the air for a certain time, it first becomes viscid, and ultimately concrete, having the appearance of animal tallow. It is in every respect similar to this substance. The exposed oil will be more or less hard, according to the time exposed; it at the same time acquires a disagreeable odour, to which we give the name rancidity. This change is more rapidly brought about by dilute nitric acid, or any substance which affords oxygen.
Of the fat vegetable oils we may mention the two most important, these being oil from rape seeds, known as rape oil; and that of cole-seeds. Rape oil is used in many instances in bearings to lessen friction. It has however a decided action upon any iron gudgeon, as we see in the axle-trees of carriages. Cole-seed oil is primarily used by wool-dressers, in order to preserve the wool from the attacks of moths; and also by leather-dressers, to make leather supple.
C. Mineral oil
An empyreumatic oil can be obtained from pit-coal by destillation. It has many properties in common with oil of turpentine or the oil of common tar. Useless for lubrication due to its volatility.
Oil of the earth, Oleum Terrae, is a thick mineral fluid with the consistence of a thin syrup, very little transparant, and of a strong penetrating smell. It oozes out of the cracks in rocks, in several parts of the island of Sumatra and some other parts of the East Indies, and is much esteemed there in paralytic disorders. No practical technical application is known at that time; the oil also is very rare in Europe.
Rees was referring to rape oil for the lubrication of bearings.